Psycho Staff Manga by Satoshi Mizukami

"To Hiiragi Kouichi-kun. I'll be waiting for you after school behind the school gym. Sakuragi Umeko." These were the words written in the first love letter Hiiragi ever received. But when he meets Sakuragi, she tells him that she wants to take him to the planet R'lyeh!?! Disappointed that the love letter from the cute girl came from a nutcase, Hiiragi returns home, only to find that Sakuragai won't give up so easily. Not only that, she may have been telling the truth afterall! But then again, Hiiragi isn't such a normal guy, either...